The present invention relates to a rolling bearing provided with a film of oil under pressure of the “squeeze film” type and intended for use, in particular, in the field of aviation.
Rolling bearings are commonly used in the field of aviation. An aviation turbomachine has rolling bearings for rotatably supporting a first shaft relative to a second shaft that is coaxial with the first. For example, such bearings may be disposed between the high pressure turbine shaft and the low pressure turbine shaft of the turbomachine. Such bearings are essentially constituted by balls or rollers retained in races formed by outer and inner rings. In a turbomachine, ball bearings are generally used for retaining axial loads and roller bearings for retaining radial loads.
In order to obtain satisfactory operation of rolling bearings of this type, it is necessary to ensure firstly that the bearings are lubricated and cooled, and secondly that vibration of the shafts and the bearings is damped.
In conventional manner, bearings are lubricated and cooled by injecting oil between the rings of the bearing. More precisely, oil is delivered between the bearing rings from an oil feed circuit connected to one or more orifices pierced in the inner ring of the bearing. The oil is then delivered or centrifuged towards the outside of the bearing, taking away the heat produced by the bearing by transfer of heat. In addition, in order to reduce the vibration generated by the high speed of rotation of the shafts of the turbomachine that are supported by said bearings, the oil under pressure is also confined between the outer ring and a structural part of the bearing via the same feed circuit. The oil under pressure is thus present in the form of a thin film at the contact surface between the outer ring and the structural part of the bearing, and it serves to act as a vibration damper. Two annular sealing rings interposed between the outer ring and the structural part of the bearing define the size of this oil film.
A problem of feeding the vibration-damping film with high pressure oil then arises in a rolling bearing disposed between two rotary shafts, for example between the low pressure turbine shaft and the high pressure turbine shaft of a turbomachine. Under such circumstances, it is difficult to feed the oil film in satisfactory manner via a conventional feed circuit. In particular, it turns out to be difficult to provide the shaft in question with a feed circuit that includes recovery scoops, feed ducts, and a pump.
U.S. Pat. No. 4,693,616 proposes a solution to this problem, which solution consists in using the pressure generated by centrifuging the lubricating oil of the bearing in order to feed the damping oil film. For this purpose, an orifice is pierced through the outer ring to open out into the contact surface between the outer ring and the structural part of the bearing. Under the effect of the centrifugal force generated by the shafts rotating, the oil injected between the rings of the bearing then penetrates via said orifice into the space that lies between the outer ring and the structural part so as to form the oil film.
However, the solution described in that patent does not enable pressures to be generated in the oil film that are sufficiently high, thereby leading to problems of filling and encouraging cavitation phenomena within the oil film. Such problems have the effect of reducing the efficiency of the turbines of the turbomachine.